The confluence of the modern Colorado River (CR) and the Little Colorado River (LCR) in Grand Canyon, looking west.
Credit: UNM UCAM Newsroom
The Nature paper proposes that the proto- Colorado River first flowed from the Little Colorado River valley through a pre-existing East Kaibab paleocanyon and began to carve Grand Canyon about 6 million years ago; Ma= million years; photo by Ted Grussing.
